SaaS providers continuously aim to optimize the costefficiency, scalability and trustworthiness of their offerings. Traditionally, these concerns have been addressed by application-level middleware platforms that implement a multi-tenant architecture.However, the recent uprise and industry adoption of container technology such as Docker and Kubernetes, exactly for the purpose of improving the cost-efficiency, elasticity and resilience of cloud native services, triggers the unanswered question whether and how container technology may affect such multi-tenant architectures.To answer this question, we outline our ideas on a container-based multi-tenant architecture for SaaS applications. Subsequently, we make an assessment of the technical Strengths, Weaknesses, Opportunities, and Threats (SWOT) which should be taken into account by a SaaS provider when considering the adoption of such containerbased architecture.

Abstract-The cloud computing paradigm promises increased flexibility and scalability for consumers and providers of software services. Service providers that exploit private cloud environments offer restricted flexibility and scalability because of the limited capacity. However, such organizations are often reluctant to migrate to public clouds because of business continuity threats and vendor lock-in. Hybrid clouds potentially combine the benefits of private and public (external) clouds. Vendor lockin can be avoided when multiple external clouds are supported and effectively exploited. This paper presents a middleware platform for hybrid cloud applications. The middleware enables organizations to control the execution of their applications in hybrid cloud environments. Driven by policies, the middleware can dynamically decide which requests and tasks are executed on a particular part of the hybrid cloud. The core of the middleware, and the focus of this paper, is an abstraction layer. The abstraction layer enables portability over multiple services including data storage, blob storage, and asynchronous task execution of various PaaS platforms as well as interoperability between the PaaS platforms. We have validated the core concept by building a prototype implementation that runs on top of specific PaaS platforms as well as on a cloudenabling middleware. A document processing SaaS application has been instantiated on the middleware. Performance results have been collected for JBoss AS cluster, Google App Engine, and Red Hat OpenShift.

Multi-tenant Software-as-a-Service (SaaS) applications are increasingly built on combinations of cloud storage technologies and providers in a so-called multi-cloud setup. One advantage is that such a setup helps satisfying the different-sometimes even contrasting-storage requirements of different customer organizations (tenants). In such a multi-cloud environment, the application data is distributed and replicated over multiple cloud storage systems, each differing profoundly in supported data models, development APIs, performance, scalability, availability, and durability. Despite the clear benefits, managing such a multi-cloud storage architecture in practice is non-trivial. Addressing this complexity in the application layer is far from ideal, as it inherently limits the flexibility with which continuously changing application-wide and tenant-specific storage requirements can be met. To alleviate this, we present a reusable data management middleware that (i) makes abstraction of multiple cloud storage technologies and thus also providers; (ii) follows a policy-driven approach for making data placement decisions; and (iii) provides tenant customization support, i.e. by allowing tenants to define storage configurations and data storage policies. We validate and evaluate our prototype implementation in the context of a realistic multi-cloud SaaS application. Our performance benchmark results indicate that the benefits of the proposed middleware can be achieved with acceptable overhead.